Pour concrete slab on the garage's old

[Lewdis]

Planning to demolish our old garage and extend the house over the garage. The question is if I can easily replace the old foundation with a new one on top.

I've tried to illustrate everything below. The red slab is our old garage slab. I'm thinking of extending it completely towards the house and also further back. Roughly estimating, I have about 30cm to build on top of the current garage slab to reach the house's height. Would it be cost-effective to build with taller edge elements where there presently are none, and then have less over the garage?

The second question is about the sewage layout. I marked in orange where the sewage exits the house today. I've also marked in green where I think I could add from a new toilet.

I would like to run it diagonally like this to avoid drilling through the entire garage slab. Is this an okay solution or will I have too many bends?

Grateful for any input on this.

 

[Lewdis]

No expert sitting on a Sunday afternoon and still has nothing else to do?

 

[prototypen]

The drainage is no problem, the municipality might want to know that you've expanded the drainage (if it is municipal)
Having two slabs on top of each other can be a problem if not compacted carefully.
How do you handle the roof drainage?

I have two slabs on top of each other in one place, but there's a lot of gravel in between and I haven't seen any problem.

Protte

 

[Lewdis]

The drain is not an issue, the municipality might want to know that you have expanded the drainage (if it is municipal). Having two plates on top of each other can be a problem if not tamped carefully. How are you dealing with roof drainage?

I have two plates on top of each other in one spot, but there's a lot of gravel in between, and I haven't seen any problems.

Protte

Thanks for your inputs. I'm not quite finished with how the extension should look, but one idea is to build a sloped roof down from the existing house. This would then go down where the garage's old pipes are. I might have to replace those as well. There are no such pipes between the house and the garage as everything has gone down at the front.